Recording engineers use various techniques, depending on the nature of a recording (e.g., live or studio), to include “ambience” components in a sound recording. Such components may be included, for example, to give the listener a sense of being present in a room in which the primary audio content of the recording (e.g., a musical performance or speech) is being rendered.
Ambience components are sometimes referred to as “indirect” components, to distinguish them from “direct path” components, such as the sound of a person speaking or singing, or a musical instrument or other sound source, that travels by a direct path from the source to a microphone or other input device. Ambience components, by contrast, travel to the microphone or other input device via an indirect path, such as by reflecting off of a wall or other surface of or in the room in which the audio content is being recorded, and may also include diffuse sources, such as applause, wind sounds, etc., that do not arrive at the microphone via a single direct path from a point source. As a result, ambience components typically occur naturally in a live sound recording, because some sound energy arrives at the microphone(s) used to make the recording by such indirect paths and/or from such diffuse sources.
For certain types of studio recordings, ambience components may have to be generated and mixed in with the direct sources recorded in the studio. One technique that may be used is to generate reverberation for one or more direct path sources, to simulate the indirect path(s) that would have been present in the case of a live recording.
Different listeners may have different preferences with respect to the level of ambience included in a sound recording (or other audio signal) as rendered via a playback system. The level preferred by a particular listener may, for example, be greater or less than the level included in the sound recording as recorded, either as a result of the characteristics of the room, the recording equipment used, microphone placement, etc. in the case of a live recording, or as determined by a recording engineer in the case of a studio recording to which generated ambience components have been added.
Therefore, there is a need for a way to allow a listener to control the level of ambience included in the rendering of a sound recording or other audio signal as rendered.
In addition, certain listeners may prefer a particular ambience level, relative to overall signal level, regardless of the level of ambience included in the original audio signal. For such users, there is a need for a way to normalize the output level of ambience so that the ambience to overall signal ratio is the same regardless of the level of ambience included in the original signal.
Finally, listeners with surround sound systems of various configurations (e.g., five speaker, seven speaker, etc.) need a way to “upmix” a received audio signal, if necessary, to make use of the full capabilities of their playback system, including by generating audio data comprising an ambience component for one or more channels, regardless of whether the received audio signal comprises a corresponding channel. In such embodiments, listeners further need a way to control the level of ambience in such channels in accordance with their individual preferences.